Manganosite is a rare manganese oxide that typically occurs as small, emerald green to black crystals or granular masses. It is highly sensitive to atmospheric moisture and oxidation, often altering to hausmannite or pyrolusite when exposed, requiring careful storage for collectors.
Is this manganosite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch manganosite with a known reference. Manganosite sits at Mohs 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to adamantine, dull on exposure.
- 4Match the color rangeCompare against the expected color range: green, greenish black.
- 5Look at form & habitCrystal system: cubic. Typical habit: massive.
Often confused with
Manganosite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Manganosite leaves brown, Wüstite leaves black; luster reads vitreous to adamantine, dull on exposure on Manganosite and metallic on Wüstite.
How to tell apart: Streak differs, so Manganosite leaves brown, Periclase leaves white.
Often found alongside manganosite
Minerals reported to co-occur with manganosite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MnO
- Mohs hardness
- 5.5
- Density
- 5.364 g/cm³
- Colors
- Streak
- Brown
- Luster
- Vitreous to adamantine, dull on exposure
- Transparency
- Transparent
- Crystal system
- Cubic
- Crystal habit
- Massive
- Cleavage
- {001}, fair; {111}, parting
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An alteration product of rhodochrosite or other manganese minerals, formed during oxygen-deficient metamorphism of manganese-bearing deposits; in marine manganese nodules
Where rockhounds find manganosite
Classic worldwide localities
- Franklin, Sussex Co., New Jersey, USA
- Långban and Nordmark, Värmland, Sweden
- Roughton Gill, Caldbeck Fells, Cumbria, England
- Noda-Tamagawa mine, Iwate Prefecture, and the Hamayokokawa mine, Nagano Prefecture, Japan
- Manako, Oashi, Kaso, and Hikoma mines, Tochigi Prefecture, Japan
- Taguchi mine, Aichi Prefecture, Japan
Field-hunting tip
Where it forms: An alteration product of rhodochrosite or other manganese minerals, formed during oxygen-deficient metamorphism of manganese-bearing deposits; in marine manganese nodules. If you start seeing pyrochroite, manganite, dolomite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
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Find manganosite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
